1. © 2012 Delmar, Cengage Learning Engine Diagnosis and Service: Piston, Piston Rings, Connecting Rod, and Engine Balancing Chapter 54

2. © 2012 Delmar, Cengage Learning Objectives Analyze wear and damage to the piston, piston rings, and connecting rod Select and perform the most appropriate repairs to the piston, piston rings, and connecting rod Explain the theory of engine balancing

3. © 2012 Delmar, Cengage Learning Introduction Complete rebuilt engine assemblies –Commonly installed in the industry Sometimes a piston ring will break or an engine is overheated –Piston rings: replaced whenever engine is disassembled Pistons are often reused –Connecting rods: do not usually require service

4. © 2012 Delmar, Cengage Learning Piston Service Important steps –Use a vice to hold piston and rod assembly –Remove compression rings with a ring expander –Top of the piston is cleaned on a wire wheel, with a scraper, or with an abrasive disc –Clean ring grooves with a ring groove cleaner –Use ring to double-check for correct groove depth –Check the top ring groove for excessive wear –Measure piston Place to measure varies among manufacturers

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9. Piston Service (cont'd.) Replacement pistons –Designed to weigh the same as originals Piston wear –Scuffing: caused by excessive heat –Four-corner scuffing: both skirts scuffed on edges next to piston pin

10. © 2012 Delmar, Cengage Learning Piston Ring Service Causes of piston ring wear –Leftover honing grit –Running engine with missing or damaged air cleaner –Contaminated oil fill funnel Engine is rebored –Oversized pistons and rings are used Check ring end gap –Before installing rings in a cylinder bore

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12. Installing Pins in Connecting Rods Pin press –Separates pressed-fit pins and pistons from their connecting rods Reinstallation is done using a rod heater to heat the eye of the rod

13. © 2012 Delmar, Cengage Learning Installing Rings on Pistons First –Install oil rings Second –Install the second compression ring Third –Install the top ring

14. © 2012 Delmar, Cengage Learning Oil Ring Installation Most automobiles use three-piece oil control rings Compression ring installation –Installed with identification marks facing up –Use a ring expander to install compression rings Compression ring gap position –Manufacturers specify different gap positions

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17. Connecting Rod Service Important points –Be sure to keep rod cap rods in order Upper and lowered pieces should be numbered –Examine all piston skirts Connecting rod resizing –Pressed-fit rod bolts are pressed or pounded out –Small amount of metal is ground off the rod and cap mating surfaces –Rod cap is reinstalled and the nuts torqued –Rod bore is honed

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20. Engine Balancing Service Done by a machine shop or a balancing specialist –Reciprocating parts: balanced to weigh approximately the same amount –Rotating parts: balanced by spinning on a balancing machine Heavy counterweights –Lightened by drilling Internal balancing –Achieved by drilling holes on the counterweights

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23. Engine Balancing Service (cont'd.) Bob weights –Used when spinning crankshaft to simulate correct weight Replacement piston balance –Critical in V-type engines Balance shafts –Must be replaced in the proper manner to maintain balance

24. © 2012 Delmar, Cengage Learning Advanced Balancing Information Types of vibration –Primary vibration –Rocking couple –Secondary vibration Types of imbalance –Force (i.e., static or kinetic) imbalance –Dynamic and couple imbalance

25. © 2012 Delmar, Cengage Learning